Turbogenerator with internal liquid cooling of exciter winding



Dec. 3o. 1969 E. wma-MANN am 3,487,243

TURBOGENERATOR WITH INTERNAL LIQUID COOLING OF EXCITER WINDING I VVEVRS Eugen edemamn Rolf-Dieer Kranz, B Werner Sark J JW x. im@

A-hornegs Dec. 30, 1969 E, WIEDEMANN ETAL 3,487,243

TURBOGENERATOR WITH INTERNAL LIQUID COOLING OF EXCITER WINDING Filed Oct. 20, 1967 2 Sheets-Sheet 2 Byp- AUnited States Patent Oiltice 3,487,243 Patented Dec. 30, 1969 3 487 243 TURBOGENERATORWITH INTERNAL LIQUID COULING F EXCITER WINDING Eugen Wiedemann and Rolf-Dieter Kranz, Baden, and

Werner Sark, Birr, Switzerland, assignors to Aktiengesellschaft Brown, Boveri & Cie, Baden, Switzerland, a joint-stock company Filed Oct. 20, 1967, Ser. No. 676,775 'Claims priority, application Switzerland, Oct. 27, 1966, 15,595/ 66 Int. Cl. H02k 9/20 U.S. Cl. 310--54 9 Claims ABSTRACT OF THE DISCLOSURE A turbogenerator of the type wherein the exciter Winding on the rotor is directly, i.e. internally cooled by circulation of a liquid coolant, provides for removal of lost heat at the surface of the rotor and at the end caps thereof by means of liquid cooling lines extending axially outside of the rotor body and under the end caps for the entire length of the winding heads, these lines being connected into the liquid cooling 4system provided for the exciter winding.

The present invention relates to turbogenerators of the type wherein the exciter winding on the rotor is internally, i.e. directly cooled by means of a liquid coolant flowed through the winding, and 'which provides for an improved arrangement for removing lost heat at the surface of the rotor and at the end caps.

In turbogenerators, as is known, eddy currents which produce lost heat are induced on the rotor surface by harmonies of the air gap field and in case of non-symmetric load (slanting load) of the machine. To these eddycurrent Vlosses at least a part of the friction losses produces in the rotor must be added.

When a gas-cooled generator is concerned, these losses are eliminated by the gas circulating in the air gap. In turbogenerators, however, where the rotor winding is cooled directly, i.e. internally with a liquid, e.g. water or oil, and where no gas cooling is applied at all, the mentioned heat removal in the air gap then does not occur.

By separating the rotor zone from the stator zone by means of a -cylindrical air gap establish by a cylindrical sleeve interposed between the two so that the pressure within the rotor zone can be reduced in relation to the atmosphere, it is possible to reduce the surface friction losses. However, this has no influence on the eddy current losses produced on the rotor surface. It would be conceivable, therefore, to transfer this lost heat to the cooling liquid circulating in the rotor winding. However, the temperature gradient across the winding insulation becomes impermissibly high, especially at slanting load.

It is known also how to cool the rotor teeth directly with liquid through bored or cut channels. But frequently the tooth is mechanically very highly utilized; moreover, especially in the case of one-piece rotor bodies, the drilling of relatively small but long holes presents great manuacturing diiculties, While cut channels must be welded shut again, which is possible only with special thermal measures in view of the generally poorly welding rotor material.

It must further be taken into account that additional losses occur not only at the surface of the rotor but also at the rotor end cap, which is provided with a reinforced electric insulation against the exciter winding. An intense temperature rise of the rotor cap leads to loosening of the shrink lit of the cap and hence to unsteady running of the generator. Neither can these additional losses be eliminated by the measures already mentioned.

The present invention relates to a turbogenerator with exciter winding directly cooled with liquid and without gas renewal in the air gap, where the lost heat at the surface of the rotor and at the rotor end caps is removed in a very simple and eifective manner. According to the invention, this is achieved in that above the exciter conductors in the rotor grooves, axial cooling lines are provided, Which extend outside the rotor body and under the rotor end caps for the entire length of the winding head and are connected to the cooling system provided for liquid cooling of the exciter winding.

With reference to the accompanying drawings, two embodiments of the invention are explained in further detail. FIGS. l and 2 sho-w the ro-tor of a turbogenerator for each embodiment partially in longitudinal section, while the corresponding liquid cooling system is illustrated schematically in FIGS. 3 and 4. FIGS. 5 and 6 each show a transverse section through a rotor groove.

In FIG. 1, where for the sake of simplicity only the parts required for comprehension of the invention are shown, 1 denotes the rotor and 2 the exciter winding, which is cooled directly and internally with a liquid, for example water. For the retention of the winding heads 3 at each end of the exciter winding 2, each rotor end is provided with a flying rotor cap consisting of a ring 4 which is shrink-tted on the one hand onto the rotor body 1, and on the other hand, is firmly connected with an annular end plate 5 by a shrink t. The conductors in winding heads 3 communicate via the conduits 6 with a water distribution chamber 7 which is subdivided into several tangential sub-chambers. The connections of the conduits 6 to the chamber 7 can be bushed to electrically insulate them from each other. These sub-chambers are connected in known manner via radially extending pipe sections to concentric channels provided in the rotor shaft, which channels serve to supply and remove the cooling water. Between the rotor 1 and the stator, not shown, a cylindrical air gap established by a sleeve 10 is provided, so that the pressure in the rotor zone located inwardly of sleeve 10 can be reduced in relation to the external atmosphere in order to reduce the friction losses very substantially.

Outwardly of the exciter conductors 2, hollow rods 11, 11 are provided in the rotor grooves which extend outside the rotor iron 1 and under the rotor cap rings 4 for the full length of the Winding heads 3. Thus these hollow rods extend from one end of the rotor winding to the other, including the end caps. On the non-drive side of the rotor, the hollow rods 11 communicate with each other via a tangentially subdivided annular line or manifold 12 and are fed with cooling water from the water distribution chamber 7 via inow pipe sections 13. In an annular line or manifold 15 provided on the drive side of the rotor, the hollow cooling -rods 11 are also the hollow cooling rods 11 serving for the return flow of the cooling liquid communicate with each other. The cooling liquid thus flows back through these cooling rods 11 to the respective parts of the annular line 12 and thence via the outflow pipe sections 13 to the Water distribution chamber 7.

As is evident from FIG. 3, the annular line 12 is subdivided inthe present case into four equal sectors, two each serving to supply and to remove cooling liquid. Alternatively, several pipe line sections 13, 13 may be provided per sector. By 16 is indicated the subdivision of the distribution chamber 7.

In the embodiment according to FIGS. 2 and 4, the rotor is legended 1', the rotor exciter Winding 2', and the winding heads 3. The winding heads 3 are held by a rotor cap for each, consisting of a cap ring 4' and an end plaie S', and communicate via the conduits 6 with a tangentially subdivided water distribution chamber 7'.

Outwardly of the exciter winding 2', again hollow rods 20 are provided in the rotor grooves. Between rotor 1 and the stator, not shown, there is a cylindrical air gap sleeve In this embodiment, as is evident from FIG. 4, the cooling water supply from the distribution chamber 7 occurs via conduits 21 of magnetic material which are placed into the pole zone in the active rotor iron and open into an annular line 22 on the drive side of the rotor, from whence all hollow rods 2t) are fed with cooling liquid. On the non-drive side, the cooling rods 20 likevwise communicate with an annular line 23, subdivided for example into two sectors, which in turn communicate through pipe sections 24 with the outflow portion of the annular chamber 7. The annular lines 22, 23 can be divided at most into as many sectors as there are pipe connections 21, 24.

Since, in contrast to the hollow conductors of the exciter winding, in the cooling arrangement according to the invention, the cooling rods 11, 11 (FIG. 1) or respectively 20 (FIG. 2) need not be fed with cooling liquid via electrical insulation members, it is possible to solder or weld the cooling rods at the end directly to an annular line which latter requires only a relatively small number of pipe connections for communication with the distribution chamber arranged outside the rotor cap. The result of this is that any weakening of the distribution chamber wall is much less than what would be the case were each cooling rod to be connected individually with the distribution chamber 7.

FIGS. 5 and 6 illustrate in transverse section two forms of construction of the hollow cooling rods which, according to the invention, are provided for the removal of the lost heat at the surface of the groove wedges and at the tooth surface.

In `both figures, the hollow cooling rod inserted in the groove between the exciter conductors 2 and the Wedge 30 located at the entrance to the groove is legended 31 and consists, for example, of copper. Since it is obvious that the hollow cooling rods 31, correspondingly numbered 11, 11 and 20 in FIGS. l and 2 do not form part of the exciter winding conductors 2, i.e. they are independent of such winding, they are not required to be insulated. This is obvious from the detailed views in FIGS. 5 and 6 where there is a direct heat transfer path to the bare, i.e. uninsulated hollow rod 31 through the wedges 32 from the rotor iron. A similar essentially direct heat transfer path exists from the inner surface of the end cap 4 to the bare hollow rod or cooling lines 11, 11', 20 as seen in FIGS. 1 and 2. To obtain `good heat conduction to the rotor surface, wedge-shaped pieces 32 are fitted on both sides of the cooling rod into corresponding recesses; they apply against the groove wall and against the cooling rod by inherent centrifugal force. In FIG. 5, the recesses for the wedge-shaped pieces 32 are provided in the cooling conductor 31 itself, and in FIG. 6, in the groove wall. The embodiment according to FIG. 6 is used when the area within the cooling rod provided for flow of cooling lmedium is large and not enough cross section of the rod remains to resist the pressure exerted by the centrifugal force of the groove filling. Good heat transfer from the tooth directly into the cooling rod is of particular advantage especially when the wedge is made of non-magnetic steel and has a low conductivity.

If the cooling rods 31 are made, for example, of stainless steel, it is advantageous to provide a damper rod 33 between the cooling rods 31 and the groove Wedge 30, as indicated in FIG. 5.

We claim:

1. In a turbogenerator structure wherein hollow conductors of an exciter winding are located in longitudinally extending wedge-closed grooves in the rotor element thereof and are directly cooled by flowing a liquid coolant through the hollow conllrlctgrs,g and wherein the winding heads at opposite ends of the winding are covered by metallic end caps, the improvement wherein non-insulated metallic hollow cooling rods independent of said exciter winding are located in said rotor grooves adjacent the wedges, said cooling rods being extended beyond the ends of said rotor grooves into the space between each end cap and the corresponding winding head, said cooling rods extending for the length of said winding head and end cap adjacent the inner surface of said end cap, and being connected into the liquid cooling system provided for said exciter winding, said hollow rods thereby being in essentially direct heat transfer relation with the rotor iron and wedges adjacent the surface of the rotor and with the inner surface of said end caps.

2. A turbogenerator structure as defined in claim 1 and which further includes a cylindrical sleeve surrounding the surface of said rotor and establishing an annular air gap therebetween.

3. A turbogenerator structure as defined in claim 1 wherein said hollow cooling rods are connected at each end thereof into a common annular manifold provided in the zone of the corresponding winding head, and wherein said annular manifolds communicate with the liquid cooling system provided for said exciter winding.

4. A turbogenerator structure as defined in claim 1 wherein said cooling rods communicate with each other on the drive end of said rotor via a common annular manifold provided in the Zone of the corresponding winding head and which is fed directly with liquid coolant from the inflow side of the cooling system for said exciter winding via conduits inserted in the pole zone of said rotor, and wherein said cooling rods also communicate with each other at the other end of said rotor by another annular manifold which is connected through pipe sections with the outflow side of the cooling system provided for exciter winding.

5. A turbogenerator structure as defined in claim 4 wherein the rotor grooves in the pole zone provided for the inow conduits, also cooling rods above the inflow conduits are provided.

6. A turbogenerator structure as defined in claim 5 wherein said inflow conduits are made from a magnetic material.

7. A turbogenerator structure as defined in claim 1 wherein said cooling rods consist of copper.

8. A turbogenerator structure as defined in claim 1 wherein said cooling rods consist of stainless steel and wherein a damper rod is placed between the cooling rod and the wedge element which closes off the entrance to the rotor groove.

9. A turbogenerator structure as defined in claim 1 and which further includes wedge-shaped elements inserted between the wall of the rotor groove and the cooling rods, said wedge-shaped elements serving to establish good thermal contact between the cooling rod and the rotor tooth by the centrifugal forces derived from rotor rotation.

References Cited UNITED STATES PATENTS MILTON O. HIRSHFIELD, Primary Examiner R. SKUDY, Assistant Examiner 

